React-Native: Application has not been registered error

I guess it is an error caused by not matching name of project and your registered component.

You have inited project with one name, i.e.

react-native init AwesomeApp

But in your index.ios.js file you register other component

AppRegistry.registerComponent('Bananas', () => Bananas);

When it must be

AppRegistry.registerComponent('AwesomeApp', () => Bananas);

If your component name does match, ensure you don't have any other react-native/node process running in another terminal.

Modify MainActivity in android/app/src/main/java/com/your-package-name/MainActivity.java like this,

@Override
protected String getMainComponentName() {
    return "Bananas"; // here
}

Most of the times the problem is that you have another react-native start (i.e. React Native Packager) server running either on another terminal or another tab of TMUX (if you are using TMUX).

You need to find that process and close it, so after running react-native run-ios for instance, it will establish a new packager server that registered for that specific application.

Just find that process using:

ps aux | grep react-native

find the process id (PID) and kill the packager process using kill command (e.g. kill -9 [PID]). You should find the launchPackager.command app in macOS, not sure about the other operating systems.

Then try to run the run-ios (or android) again. You should be able to see the new path after running the new packager server, e.g.:

Looking for JS files in
   /Users/afshin/Desktop/awesome-app